This invention relates to a parking assembly and more particularly, to a parking assembly which is adapted for use with a vehicle, which utilizes a servo mechanism to selectively engage and disengage the park gear of the vehicle, and which allows the parking event to be calibrated to minimize disengagement noise, to prevent engagement under certain undesirable conditions, and to tailor shift efforts.
Parking mechanisms or assemblies are used in automotive vehicles to allow the vehicle to enter into and maintain a xe2x80x9cparkedxe2x80x9d condition or state. Parking assemblies typically include a park rod or cam which selectively actuates a parking pawl which operatively engages the vehicle""s park gear, thereby maintaining the vehicle in a xe2x80x9cparkedxe2x80x9d position or state.
The park rod is typically mechanically linked to the vehicle""s shifter and moves in response to shifter movement. When the shifter is moved to the xe2x80x9cparkxe2x80x9d position, a cam which is disposed on the park rod engages the xe2x80x9cparking pawlxe2x80x9d which pivots or rotates into a position where it is disposed between a pair of teeth on the park gear, thereby substantially preventing the park gear and the output shaft from further rotating.
The park rod includes a spring which is sometimes compressed during the engagement with the parking pawl. Particularly, the spring within the park rod is compressed only during certain shifts into park. For instance, when the park rod cam engages the parking pawl and causes it to pivot into the park gear, the parking pawl is sometimes pivoted into and forcibly abuts a tooth of the park gear. During these types of shifts, the pivotal movement of the parking pawl is temporarily limited or stopped, thereby preventing further movement of the cam until the park gear is rotated and causing the spring within the park rod to be compressed. When the park gear rotates, the parking pawl slides along the tooth which it abuts until it xe2x80x9cdrops intoxe2x80x9d or is forced into a space between teeth of the park gear. During other shifts into the park position, the parking pawl is engaged by the cam and is rotated or pivoted directly into a space between gear teeth. During these types of shifts, the path of travel of the park rod is substantially unobstructed and the spring within the park rod is not compressed. The resulting inconsistency of spring compression causes the force required to shift the vehicle into park to vary from shift to shift. Because the shifter is mechanically coupled to the park rod in these prior systems, the user or driver of the vehicle undesirably xe2x80x9cfeelsxe2x80x9d or experiences inconsistent or different forces at the shifter when shifting the vehicle into park. Furthermore, when shifting a vehicle out of the park position while the vehicle is disposed on an incline, the loading of the park pawl will vary with the loading of the vehicle. This causes the park xe2x80x9cpull outxe2x80x9d load to vary based upon the vehicle weight and incline. This load variation is likewise undesirably experienced by an operator of the vehicle.
Another drawback with these prior mechanical systems occurs when a driver inadvertently shifts into park while the vehicle is still moving. Particularly, if the vehicle is moving above a certain speed, the parking pawl may not fully engage the park gear, but rather xe2x80x9cratchetsxe2x80x9d against the gear, thereby creating an unaesthetic sound and vibration and potentially damaging the parking pawl and park gear. Moreover, when residual torque remains within the output shaft during a parking event (e.g., when the vehicle is parked on an inclined or declined surface), the park gear imparts a torsional force or load on the parking pawl which may be transmitted through the park rod and may result in undesirable vibrations which can be xe2x80x9cfeltxe2x80x9d or experienced at the vehicle""s shifter.
Vehicles which utilize a xe2x80x9cshift by wirexe2x80x9d system, where the shifter is mechanically coupled to and actuates the park rod by use of a wire or cable, suffer from other drawbacks. By way of example and without limitation, the cable may act as a noise and/or vibration path or medium which generates undesirable noise and/or vibration that can be experienced within the passenger compartment.
There is therefore a need for a new and improved parking assembly for use in a vehicle which overcomes many, if not all, of the previously delineated drawbacks of such prior parking assemblies.
A first advantage of the invention is that it provides a calibratable parking assembly which overcomes at least some of the previously delineated drawbacks of prior parking assemblies.
A second advantage of the invention is that it allows the parking event to be calibrated based upon various selectable vehicle conditions and/or attributes.
A third advantage of the invention is that it provides for a consistent load at the vehicle""s shifter assembly each time the vehicle is shifted into and out of park.
A fourth advantange of the invention is that it prevents the vehicle from being shifted into park under certain conditions.
According to a first aspect of the present invention, a parking assembly is provided for use in combination with a vehicle of the type having a park gear and a shifter which is selectively movable into a park position. The parking assembly includes a pawl member which is selectively movable between a first position in which the pawl member is remote from the park gear, and a second position in which the pawl member engages the park gear; a park rod or cam which selectively engages the pawl member effective to cause the pawl member to move from the first position to the second position, and which selectively disengages the pawl member effective to cause the pawl member to move from the second position to the first position; and a servo assembly which is coupled to the park rod and which is effective to selectively move the park rod in response to movement of the shifter, thereby causing the park rod to engage and disengage the pawl member.
According to a second aspect of the present invention, a method is provided for selectively engaging a parking assembly in a vehicle of the type having a park gear and a parking pawl which selectively engages the park gear. The method includes the steps of: providing a servo assembly; providing a member for selectively contacting the parking pawl; coupling the member to the servo assembly; and selectively activating the servo assembly to cause the member to engage the parking pawl thereby causing the parking pawl to engage the park gear.